This core will recruit , screen, and perform diagnostic evaluations on participants to be included in the other projects. This core will continue to follow participants recruited in the previous funding cycle (1992 cohort). In addition, 2000 new participants (1999 cohort) will be recruited to supplement the existing cohort. Like the 1992 cohort, the 1999 cohort will be recruited from an enumerated listing of Medicare recipients provided to us by the Health Care Finance Administration (HCFA). Evaluation procedures will parallel those of the previous funding cycle. At each visit, all participants receive a detailed interview to assess cognitive and functional impairment and a neuropsychological evaluation. Subjects screening positive for stroke, Parkinson's disease, or cognitive impairment also will receive a standardized medical and neurological evaluation. Data from all subjects are reviewed at a diagnostic consensus conference of neurologists and neuropsychologists. The diagnosis of dementia is made based upon evidence of cognitive impairment on neuropsychological testing and functional impairment sufficient to interfere with social or occupational functioning. It a participant is demented than the cause of dementia will be specified further. Cranial MRI scanning has been added to better assess the contribution of cerebrovascular disease in incident dementia cases. The severity of cognitive deficit in non-demented subjects also is rated. We will continue to examine the influence of sociocultural factors on our diagnostic paradigm. We have incorporated measures of educational experience and literacy into this core to permit assessment of these variables on our diagnostic process.